1. Field of the Invention
The present invention relates to a buffer system for adjusting first-in first-out, and more particularly, to a buffer system that temporarily stores a plurality of substrates and is capable of adjusting first-in first-out.
2. Description of the Related Art
In general, a buffer apparatus refers to an apparatus that temporarily stores substrates during a series of processes in a semiconductor process or a process of manufacturing flat panel displays. When time varies depending on a process to be performed in a series of processes or any one of the processes temporarily stops, the buffer apparatus may provide a space where substrates in other processes can temporarily stay. For example, the buffer apparatus may be used between a cleaning process and a thin film deposition process, or between the cleaning process and an inspection process, which are performed at different operating speeds to adjust operation time of the entire manufacturing process.
FIG. 1 is a schematic view illustrating a buffer apparatus according to the related art.
The known buffer apparatus has therein a vertically movable transfer unit to store substrates that are transferred to the buffer apparatus, and moves the substrates to an upper portion thereof. As a result, the substrate transferred first is positioned at the upper portion of the buffer apparatus. Therefore, in order to transfer the substrates stored in the buffer apparatus to a process apparatus of the next process, the lowermost substrate is transferred first. This is because a device for transferring a substrate is driven by the rotation of rollers that are mounted to the lowest shafts.
As a result, since the substrate entered first is transferred last, the substrate entered first stays relatively longer in the buffer apparatus. As the substrate stays longer in the buffer apparatus, dust or a foreign substance may be adhered to the substrate. Further, although though the substrate needs to undergo the next process after the previous process before a predetermined time, the next process is performed even after the predetermined time, which results in low yield.
In addition, a system for individually transferring substrates by a robot to adjust first-in first-out needs an expensive robot, which increases the manufacturing cost.